/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nutch.indexer.metadata;

import java.util.HashMap;
import java.util.Map.Entry;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Text;
import org.apache.nutch.crawl.CrawlDatum;
import org.apache.nutch.crawl.Inlinks;
import org.apache.nutch.indexer.IndexingException;
import org.apache.nutch.indexer.IndexingFilter;
import org.apache.nutch.indexer.NutchDocument;
import org.apache.nutch.parse.Parse;

/**
 * Indexer which can be configured to extract metadata from the crawldb, parse metadata or content metadata.
 * You can specify the properties "index.db", "index.parse" or "index.content" who's values are
 * comma-delimited <value>key1, key2, key3</value>.
 */

public class MetadataIndexer implements IndexingFilter {
	private Configuration conf;
	private HashMap<String, String[]> staticfields;
	private static String[] dbFieldnames;
	private static String[] parseFieldnames;
	private static String[] contentFieldnames;
	private static final String db_CONF_PROPERTY = "index.db.md";
	private static final String parse_CONF_PROPERTY = "index.parse.md";
	private static final String content_CONF_PROPERTY = "index.content.md";

	public NutchDocument filter(NutchDocument doc, Parse parse, Text url,
			CrawlDatum datum, Inlinks inlinks) throws IndexingException {

		// just in case
		if (doc == null)
			return doc;

		// add the fields from crawldb
		if (dbFieldnames != null) {
			for (String metatag : dbFieldnames) {
				Text metadata = (Text) datum.getMetaData().get(
						new Text(metatag));
				if (metadata != null)
					doc.add(metatag, metadata.toString());
			}
		}

		// add the fields from parsemd
		if (parseFieldnames != null) {
			for (String metatag : parseFieldnames) {
				String value = parse.getData().getParseMeta().get(metatag);
				if (value != null)
					doc.add(metatag, value);
			}
		}

		// add the fields from contentmd
		if (contentFieldnames != null) {
			for (String metatag : contentFieldnames) {
				String value = parse.getData().getContentMeta().get(metatag);
				if (value != null)
					doc.add(metatag, value);
			}
		}

		return doc;
	}

	public void setConf(Configuration conf) {
		this.conf = conf;
		dbFieldnames = conf.getStrings(db_CONF_PROPERTY);
		parseFieldnames = conf.getStrings(parse_CONF_PROPERTY);
		contentFieldnames = conf.getStrings(content_CONF_PROPERTY);

		// TODO check conflict between field names e.g. could have same label
		// from different sources

	}

	public Configuration getConf() {
		return this.conf;
	}
}
